Devices for elevating and lowering a vehicle, or a desired supported portion thereof, relative to a ground surface are well known in the art. In their most basic form, such devices consist of well known shock absorber assemblies or telescopic forks, often deployed in conjunction with helical springs, that connect the supported portion to, and above, wheels of the vehicle which operate on the ground surface. The supported or suspended portion is generally connected to and supported above the wheels by the device.
Such basic devices retract in response to force shocks encountered by wheels during navigation on a ground surface, for example driving over a bump or a hole in the ground surface, thus lowering the supported portion relative the wheel and often relative the ground surface. The device then extends again to raise the supported portion relative the wheel and the ground surface. The overall effect is at least partial absorption, i.e. dampening, of the shocks and thus a more stable ride for the supported portion of the vehicle relative the ground surface. Typically, users of the vehicle are situated on or in the supported portion, and thus enjoy a smoother ride.
However, while such basic suspension devices provide basic stability for the vehicle, they provide very little, if anything, for adjusting the elevation of the supported portion relative the wheels and the ground surface in response to varying levels of speed of the vehicle. For example, it is often advantageous, particularly for two wheel vehicles such as motorcycles, that the supported portion be as close to the ground surface as possible to provide a lower center of gravity and additional stability, especially for short drivers, compared to normal vehicle height at normal low driving speeds. On the other hand, at higher speeds, it is also often preferable to lower the supported portion to provide a lower center of gravity and better steering and handling around curves. Thus, it is desirable that a vehicle suspension device allows the supported portion to be raised and lowered, based on speed of the vehicle, while still providing unaltered shock absorption characteristics.
For example, US Patent Application Publication No. 2009/0045595 A1 teaches a device in which a control sleeve, having a spring attached to a ring flange at a lower end of the control sleeve and to the wheel or frame, may be raised and lowered on a shaft by a motor, thus raising and lowering the supported portion above the device. However, this device offers little shock absorption capability in the lowered configuration. Furthermore, such a vehicle height adjustment device would need to be significantly reinforced and thereby becomes bulky and heavy in order to undergo severe bending and lateral efforts when a separate shock absorber assembly is mounted on the ring flange adjacent and parallel to the spring for suitable dampening and stability. U.S. Pat. No. 4,568,101 issued to Bleustein et al. teaches a device in which a compressor is connected to pneumatic or hydraulic shock absorbers of a vehicle. As vehicle speed increases and decreases, the compressor increases and decreases pressure in the shock absorbers, thus causing them to extend and retract to raise and lower the supported portion. Unfortunately, this device requires addition of a compressor, which may be cumbersome, and which has a long reaction time delay for operating changes. Further, use of additional or reduced compression alters and may compromise shock absorbing ability of the suspension device, such that the change in vehicle height not only changes the vehicle ground clearance but also changes the suspension travel.
Furthermore, because of the altering of the suspension travel and suspension behaviors, all existing systems are significantly limited in their travel range and therefore, would not provide a sufficient lowering of the body of the vehicle relative to the ground surface for a driver (of a motorcycle for example) to notice the change in vehicle height, rendering the system inefficient.
Accordingly, there is a need for an improved vehicle height adjustment suspension device of simple and compact configuration that does not alter the mechanical behaviors of the suspension of the vehicle depending on its adjustment.